The present invention relates generally to a method of manufacturing inductor structures, and more particularly to a method of manufacturing a spiral inductor structure having a high quality factor Q, a spiral inductor structure, and a device package structure using the spiral inductor structure as a packing element.
An inductor is an impedance device typically including a coil, with or without a core, for introducing inductance to an electronic circuit. Both transformers and inductive reactors are included within the meaning of “inductor.” Various inductors are shaped as coils wrapped on various core materials such as ferrites. The core multiplies the inductance of a given coil by the “permeability” of the core material. The core typically is in the shape of a rod or toroid. To obtain very high inductance, the coil typically includes many turns. Winding the coil on a closed loop iron or ferrite core can further increase the inductance. To obtain as pure an inductance as possible the DC resistance of the winding should be reduced to a minimum.
Inductor structures can find their use in semiconductor devices. Microelectronic or semiconductor devices are typically fabricated from a semiconductor substrate over which patterned conductor layers are formed and separated by dielectric layers. As the microelectronic arts have advanced, integration levels and functionality levels have increased so that not only conventional microelectronic or semiconductor structures such as transistors, resistors, diodes, capacitors are fabricated in or for use with the semiconductor device, but less conventional structures such as inductors have also been fabricated in or for use with the semiconductor or microelectronic device. In particular, in semiconductor or microelectronic devices that are intended to be employed with high frequency applications, such as mobile communications it is common to employ inductor structures within the semiconductor or microelectronic devices.
A variety of microelectronic conductor structures have been disclosed in the prior art. Many of these structures have a spiral design that is implemented in a plane with the spiral containing one or more turns in the plane of the inductor. For example, U.S. Pat. No. 5,396,101 discloses a planar spiral microelectronic inductor structure having formed within its center a core layer.
U.S. Pat. No. 6,002,161 discloses a semiconductor device including an inductor element which includes a first conductive film pattern of a spiral configuration formed on a major face of the semiconductor substrate. A second conductive film pattern of an insular configuration is electronically connected only to the first conductive film pattern through contact holes formed in the interlayer insulation film and extending in an overlapping relationship with the first conductive film pattern.
U.S. Pat. No. 6,287,932 discloses a spiral inductor fabricated from a semiconductor substrate that provides a large inductance while occupying only a small surface area. A magnetic material is provided either above or below the inductor to increase the inductance of the inductor. Magnetic material also acts as a barrier that confines electronic noise generated in the spiral conductor to the area occupied by the spiral inductor. The inductance of a pair of stacked spiral inductors is increased by including a layer of magnetic material between the stacked spiral inductors.
All of these approaches have as common objectives to enhance the quality factor Q of the inductor, to maximize the inductive value, and to reduce the surface area over which the inductor is created. As is understood by a person skilled in the art, a Q factor of a microelectronic inductor structure is in general described in terms of a ratio of energy storage capacity within the inductor structure with respect to power dissipation within the inductor structure. However, due to conventional inductors requiring a considerable amount of space for installation and difficulty in manufacturing conventional inductors due to their complex coil structure, conventional inductors have a low quality factor Q.
For these reasons and other reasons that will become apparent upon reading the following detailed description, there is a need for an improved spiral inductor structure having a high quality factor Q suitable for integration in IC chips.